The worst will shortly be over for those regions, as a cold front moves east into eastern Ontario, Quebec and the Maritimes.

"We have improving weather in Ontario, in terms of drying out," Doug Gillham, a meteorologist at the Weather Network, said early Monday morning.

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The overnight rains that began on Sunday were from a combination of a cold front moving in from the U.S. Midwest, joining forces with moisture from the remnants of Tropical Storm Karen, which dissipated over the weekend.

Environment Canada did issue a special weather statement on Sunday, warning of the incoming rains, but no rainfall or severe thunderstorm warnings were issued, and much of southwestern Ontario saw between 10 and 20 mm of rain.

But some locations saw much higher amounts, reaching up to the 45 mm mark, as the rain moved through.